One of the basic procedures of hair styling is curling or waving hair. Early equipment, the so-called marcel iron, had a rod or barrel and a clamp that held the hair against the barrel. The hair is clamped, rolled onto the barrel, and, as the iron is heated, a curl is set into the hair. More hair curlers that are sold both for home and professional use today are modern adaptations of the basic marcel iron. The procedure for using these irons is to open the clamp, capture the hair ends between the clamp and the barrel, and then roll the curler toward the scalp so that the hair strands wrap about the barrel and clamp. Usually, the barrel is heated or incorporates a steam-generating system for heating the hair to set the curl.
It has been found that tight, well formed curls are better produced if the curling procedure is initiated with the curler near the scalp, the rolling or wrapping of the hair strands about the curling iron proceeding from the scalp outwardly toward the hair ends. This is believed to result from the fact that, in procedures where curling begins near the scalp, each convolution of the curl, including those near the scalp, are relatively small, thereby resulting in a well set, even curl. The previously mentioned fixed-barrel type of curler is very difficult to use for curling procedures initiated near the scalp. In consequence, most nonprofessionals only use a curling technique in which the curling begins at the hair ends and proceeds toward the scalp, the curl formed in progressively larger, concentric convolutions as the iron is rolled toward the scalp. In this curling method, the largest convolution of hair forming the curl is the one closest to the scalp. Thus, it is extremely difficult for a home user to achieve professional quality curling with the curling equipment that has been supplied for home use. Moreover, professionals acquire facility with equipment now available only after long experience.
Curling irons with motor-driven, rotatable barrels have been proposed. One example of a prior design is shown in U.S. Pat. No. 2,608,195 to Ledbetter. Such designs employ clamps that are biased to hold the hair against the barrel and that are manually actuated to relax the clamping of the hair to the barrel of the curler. It is believed that it would be difficult to achieve good hair curling techniques with such equipment because the clamp is manually actuated; these designs would be cumbersome and they would tend to be tiresome to use.